Control of spray water to reheater attemperators



April 11, 1961 1. J. KARASSIK 2,979,040

CONTROL OF SPRAY WATER TO REHEATER ATTEMPERATORS Filed July 2, 1957 DEAERATING HEATER LH IS 22 r0 BOILER l4- l8 9% Lf|| IO BOlLER FEED PUMP IGOR J. KARASSIK CONTROL OF SPRAY WATER TO REHEATER ATTEMPERATORS Igor J. Karassik, Maplewood, N.J., assignor to Worthington Corporation, Harrison, NJ., a corporation of Delaware Filed July 2, 1957, Ser. No. 669,664

1 Claim. (Cl. 122-459) This invention relates to a protective pressure reducing system for a spray water attemperator of a reheater in a power plant system.

Temperature control of reheated system is of the essence: first, to improve the heat rate of the modern high pressure power plant; second, to protect the reheater against failure from overheating; andthird, to protect the turbine against damage caused by high temperatures as for example, clearance difiiculties caused by excessive thermal expansion.

Accordingly a temperature controlling fluid, such as water, is usually introduced into afreheater through a spray attemperator having flow passage means associated therewith, such as spray nozzles at the throat of a venturi section. This fluid passing through the nozzles vaporizes very readily and mixes with the reheated steam to cool it to the required temperature.

Controlled introduction of the fluid is accomplished by the use of regulating means, such as a valve, in association with the flow passage means to permit injection of the fluid when the temperature in the reheater is increasing beyond a predetermined value.

In order to limit the valve size to practical dimensions and to limit the maintenance costs therein it is imperative that the pressure of the fluid acting on the said valve be limited to a pressure permitting injection of the fluid into the reheater.

In some cases, low pressure fluid has been provided by the use of a separate spray-water pump which would take its suction from the deaerating heater in open cycles or from the condensate pump discharge in closed cycles. In other installations, the required source of low pressure fluid has been diverted from an intermediate stage of the boiler feed pump.

In contradistinction to the foregoing systems the present invention provides a pressure reducing system for a spray water attemperator of a reheater which effectively reduces valve maintenance without the necessity of a separate pump or the need of modifying the boiler feed pump. 'This method is based on the principle that breaking down a high pressure differential in a series of orifices is conducive to considerably less wear and noise than if this pressure difierential is broken down through a single valve.

Accordingly it is an object of this invention to provide a pressure reducing system for a spray water attemperator of a reheater in a power plant system in order to minimize the wear on the regulating valve associated with the spray water attemperator.

Another object of this invention is the provision of a method of pressure reduction which reduces valve wear and maintenance without the utilization of a separate pump or the need of modifying the boiler feed pump construction.

It is a further object of this invention to provide a source of constant pressure fluid whereby the source may be tapped and the fluid therein may be passed through r d O 2,979,040 Patented Apr. 11, 1961 a control valve of a spray water attemperator and into the reheater to control the temperature therein.

To accomplish the above objectives the present invention provides a source of low pressure fluid for the spray water attemperator. The source being formed as for example, between a pressure reducing orifice and a regulating valve disposed in a by-pass line which communicates at one end with the discharge side of a boiler pump and at the'other end with the suction side of said pump.

While it is indicated that the fluid source is formed between a pressure reducing orifice and a regulating valve it is not intended to so limit this invention; the low pressure source as will be evident to those skilled in the art is preferably between two orifices, the downstream orifice functioning to further reduce the pressure in the by pass line to that pressure required to maintain fluid flow to the deaerating heater.

The orifices, which are preferably multiple pressure reducing orifices such as is shown in Patent No. 2,400,- 161, function to reducethe high pressure in the discharge side of the boiler feed pump; which pressure may be in the vicinity of 2500 p.s.i.g. at full load, to a substantially lesser pressure; the upstream orifice reducing to the vi- 'cinity of 500 p.s.i.g., to provide a low pressure source for use with the spray water attemperator;-the downstream orifice reducing in the vicinity of p.s.i.g. to provide flow through the regulating valve and into the suction side of the boiler feed system.

The regulating valve, disposed downstream of the orifices in said by-pass line, functions to control the flow through said line to thereby provide a source of substantially constant pressure between the orifices.

With these and other objects in view as may appear from the accompanying specification, the invention consists of various features of construction and combination of parts, which will be described in connection with the accompanying drawings, showing a diagrammatic view of the invention.

A source of substantially constant pressure cooling fluid generally designated 17 is provided for, in by-pass line 10 between an upstream orifice 18 and a downstream orifice 19 disposed therein.

Referring particularly to the drawing a by-pass line 10 is shown connected in the discharge line ll of the boiler feed pump 12 between the discharge gate valve 13, check valve 14 and the discharge outlet of the pump 15. The by-pass line 10 leads to some region of lower pressure in the boiler feed cycle, such as a deaerating heater shown diagrammatically at 16, on the suction side of the boiler feed pump 12 so that any water by-passed through the by-pass line 10 will be retained in the boiler feed cycle and returned to the suction of the boiler feed pump.

The pressure in source 17 being maintained substantially constant by flow control means 20, as for example a constant pressure valve, disposed downstream by orifice 19 and purchasable on the open market.

The valve 20 as will be evident to those skilled in the art, may be actuated to open or close by a signal, that indicates that the pressure in the source is increasing or decreasing, which signal is transmitted to said valve through pilot line 21. Accordingly flow to the low pressure side of the boiler feedwater cycle is permitted or precluded as a function of the pressure in the source 17.

The upstream orifice 1 8 is preferably a multiple pressure reducing orifice which functions, as is known in the art, to reduce the high discharge pressure through a series of orifices to a pressure that substantially minimizes wear on the control means 22 disposed in line 23 connected to the source 17 to provide fluid flow, when required, to the spray water attemperator 24 associated with 3 the reheater 25 which is disposed in the power plant cycle, as is well known in the art.

The pressure in by-pass line 10 is further reduced by orifice 19; having similar characteristics as orifice 1 8 and disposed downstream thereof, to a pressure that provides flow through the constant pressure valve 20 to the region'of low pressure in the power plant system so that the water by-passed will be retained in the system.

In operation the high pressure in discharge line 11 is reduced by the upstream orifice 18 to provide a source 17 of substantially lower pressure, which source 17 is connected to the attemperator 24 by the line 23; the fiow therethrough being automatically regulated by valve 22 to provide the proper cooling of the steam in the reheat cycle of the power plant system.

It will be understood that "the invention is not to be limited to the specific construction or arrangement of parts shown, but that these may be widely modified within the invention defined by the claim.

What is claimed is:

A power plant including a boiler, a boiler feed pump having discharge means, a valve, a reheater, throttle means for continually reducing the pressure on said valve, said valve operatively associated with said reheater to regmlate the flow of attemperation spray water to said reheater, delivery means for conducting water from said discharge means to said boiler; said throttle means comprising a by-pass line bypassing a portion of said delivery means, a conduit communicating with said by-pass line so that spray water is conducted from said by-pass line to said valve, 9. first pressure reducing orifice in said by-pass line downstream from said discharge means and upstream of said conduit, a second pressure reducing orifice in said by-pass line downstream from said conduit, an intermediate region of continual low pressure in said by-pass line between said orifices, flow control means for controlling the flow of water through said by-pass line, said control means connected in said by-pass line downstream of said second orifice, pressure sensitive signaling means communicating between said intermediate region and said flow control means auotmatically to regulate operation of said fiow control means so that the pressure is maintained substantially constant in said intermediate region.

References Cited in the file of this patent UNITED STATES PATENTS 977,427 Armstrong Dec. 6, 1910 2,018,119 Brouse Oct. 22, 1935 2,064,795 Gerdtz Dec. 15, 1936 2,155,986 Wheaton Apr. 25, 1939 2,167,299 Hartmann et al. July 25, 1939 2,293,314 Spence Aug. 18, 1942 2,550,683 Fletcher May 1, 1951 2,855,904 Schwander Oct. 14, 1958 2,881,793 Lee Apr. 14, 1959 FOREIGN PATENTS 858,479 France May 13, 1940 

